The present invention relates to a method and system for simulating processing a workpiece with a machine tool. The invention is also directed to a computer program and to a computer programmed with a computer program for carrying out the method.
Nothing in the following discussion of the state of the art is to be construed as an admission of prior art.
Machine tools are typically controlled by numeric controllers which execute an application program that has instruction steps, for example a part program according to DIN 66025. The application program determines the process flow in the machine, e.g., the travel paths of various tools.
The operating system of numeric controllers is typically a real-time operating system. Numeric controllers can also include control software to convert the instruction steps of the application program to machine-dependent control commands. The term real-time operating system indicates that this conversion takes place in real-time. The real-time operating system together with the control software forms the so-called real-time kernel. The numeric controller hence processes the application program within the real-time kernel.
As described above, the real-time kernel operates in real-time and coordinates, in particular, the movement of the machine axes as well as other travel of the machine tool in such a way that the process requested by the application program is carried out. The real-time kernel also determines the interpolation clock rate and the type of the interpolation. Accordingly, the kernel affects the actual machining process and the time required for the machining process.
For example, the effect of a parts program with a certain real-time kernel on the machining process of a workpiece could be tested initially by machining a workpiece, to then check the achieved machining accuracy and, if necessary, to correct the application program. However, this approach is obviously time-consuming, requires a substantial quantity of material, and is also expensive.
Simulation methods for machining a workpiece with a machine tool may include a computer provided with an application program to describe the machining to be performed by the machine tool in form of instruction steps. The computer executes the application program and determines, based on a simulation program for a controller of the machine tool, step-by-step machine-dependent control commands for the machine tool. The computer further determines, based on a computer-internal model of the machine tool and based on the determined machine-dependent control commands, expected actual states of the machine tool, thereby simulating execution of the machine-dependent control commands by the machine tool,
Such simulation methods are disclosed, for example, in the technical article “CAD/CAM und CIM in der Metallbearbeitung” (CAD/CAM and CIM in metal processing) by Stefan Peiker and Norbert Schrufer, published in “tz für Metallbearbeitung”, Vol. 82, No. 6/88, pages 17 to 27, or from German patent publication DE-A-100 47 928.
German patent publication DE-A-102 26 198 discloses a simulation method for a process of a processing machine, which is controlled by a stored-memory controller. In this simulation method, an application program is provided to a computer, with the application program describing the machining to be performed in the processing machine in form of instruction steps. The computer processes the application program and determines step-by-step control commands for the processing machine, based on a simulation program for a controller of the processing machine. The computer also determines, based on a computer-internal model of the processing machine and the afore-determined control commands, expected actual states of the processing machine, thereby simulating execution of the control commands by the processing machine. A similar process is also disclosed in WO-A-01/67193.
Japanese Patent Abstract to JP-A-07/084620 describes a simulation method for processing a workpiece with a machine tool, wherein an application program is provided to a computer, which describes in form of instruction steps the machining to be performed by the machine tool. By executing the application program, the computer step-by-step determines, based on a simulation program for a controller of the machine tool, machine-dependent control commands for the machine tool. A similar process is also disclosed in German patent publication DE-A-101 14 811.
The afore-described simulation programs are stand-alone programs used to simulate the actions of the machine tool. These simulation programs emulate the control software, but only partly and not in real-time. The expected actual states of the machine tool as determined by the simulation programs deviate more or less from the “true” actual states that the machine tool actually assumes when executing the application program. The information obtained with these simulation programs has therefore only limited significance.
In addition, generating the simulation programs and adapting the simulation programs to the new functionalities of the control software represent a significant programming task. Commercial versions of the simulation programs may hence be shipped much later than new control software, or not at all.
It would therefore be desirable and advantageous to provide an improved simulation method for processing a workpiece by a machine tool, which obviates prior art shortcomings and makes simulation programs that faithfully reproduce the behavior of the real-time kernel immediately available.